Home page of "filter", the email filtering program

This is the official page of "filter", an email filter program used to
take your incoming email, and automatically sort it, based on criteria like
who sent it, and what the subject line is. It runs on UNIX machines, and
other machines with a similar email distribution system.

Filter is different from procmail, in that it uses english commands. For
example:

from = "bugs@debian.org" then save /home/bolthole/debian-bugs
to = "mailings@bolthole.com" then execute "/home/bolthole/bin/redistribute"

"filter" was originally distributed with "elm", a
text-based mail reading program that runs on almost any platform.
It now compiles and runs without requiring elm.
v2.4 and newer will look in $HOME/.filter for "filter-rules"

Bug Fixes and feature changes

Added in 2.6: a "from" rule will match "From ",From:,Reply-To:, Sender:
independantly. Previously, the last header of those four would be the only
one to be checked.

Added in 2.5.1: iso-xxxx-xxx binary de-encoding for subject lines.

Added in 2.4.2: The "lines" compare now works again, I hope.
You can now ditch all email longer than 1000 lines, for example.

Added in 2.4: resend and mailinglist

Fixed since 2.2: executec and forwardc

Fixed since 2.1:
There previously was a problem compiling under RedHat.
There previously was a problem compiling under Debian.

Changes from ELM-bundled filter

Version 2.x of filter has some bugs cleaned up from the prior elm-bundled
one [considered as filter1.x].
For example, it can now handle unlimited numbers of 'to' addresses.
Also, if you run filter setgid, you are strongly encouraged to upgrade to
the latest version, for security reasons.

Version 2.1+ allows filter to recognize a different type of "mailbox" path.
It defaults to something like /var/mail/%u but you can tell it that email
gets delivered to users home directories by specifying /home/%u/inbox or
something similar.

Installing filter for your personal email

If you are paranoid about always getting your email, you might make a backup
of all your email for a while until you are happy with your filter
configuration. Backups are done by putting

/path/to/backupmbox,"|filter"

in $HOME/.forward, instead of only sending to filter.
Dont forget to periodically clean out your backup mailbox!

For some more detailed information about filter, you can download the
source, and look in the "doc" directory.

You will need a compiler (like gcc) to compile filter, before installing.
Dont worry, it's
pretty painless. Just run "./Configure", after extracting it from the
gzip'd, tar'd archive, and press 'return' a bunch of times!

Some filter tips

This section may grow over time.
Generally speaking, avoid using the delete rule, and save junk, to a junk
folder which you should scan through from time to time. Otherwise, you WILL
lose email that you would want to read.

What with all the irritating f.a.k!e.sub.jec%t_LI#nes these days, a
hopefully useful new feature is the alphasubject virtual header field.
It forces the subject line to lower case, and removes all punctuation.
A very useful rule is as follows:

Transparent forwarding

There is a new directive in filter2.4 for "transparently" resending
an email to another account. It is called, appropriately enough, 'resend'.
However, if for whatever reason it does not treat the headers like you
want, then you can always call sendmail or your local MTA directly,
as follows: